Fabrication of microoptical freeform arrays on wafer level for imaging applications

Abstract

Miniaturized imaging systems combining an ultra-compact form factor in combination with the ability of refocusing and depth imaging have gained much interest in the field of mobile imaging. Therefore, artificial compound eye cameras are an extremely promising approach for the realization of compact monolithic camera modules on wafer level. Up to now, their imaging performance was limited to low resolution in the range of VGA format according to fabrication constrains given by the established microoptical fabrication methods, namely the reflow of photoresist. In order to overcome these classical limitations, the use of refractive freeform arrays (RFFA) instead of conventional microlens arrays is inevitable. To enable high volume and cost efficient mass production of artificial compound eye cameras for mass markets like the consumer electronics industry, their fabrication on wafer level is essential, but has not been published up to now. We present a wafer level based process chain enabling the fabrication of these elements for the first time.

Recent advancements in optical microstructure fabrication through glass molding process

“…1) Freeform microstructure fabrication Optical systems using freeform lenses are becoming a viable solution to both imaging and nonimaging optics because of their capability to reduce the number of elements in an optical system and accurately control light irradiation. A freeform lens is loosely defined as an optical element that is not symmetric around its optical axis [76][77][78][79][80].…”

Freeform surface compensation design for machining error of primary mirror

“…Freeform surface developed rapidly and widely used in recent years, which provide a solution for the mentioned new technology. The freeform surface in optical design generally refers to the optical surface without axial rotation symmetry or translation symmetry constraints [5][6][7][8][9][10]. There are many mathematical descriptions of freeform surfaces including XY polynomial, Zernike polynomial, Q polynomial, non-uniform rational basis spline (NURBS), etc [5][6][7].…”

“…Orthogonal zernike polynomials have excellent mathematical characteristics, and their items correspond to optical aberrations. They are widely used in freeform surface expression, wavefront analysis and system aberration evaluation [8][9][10]. Interferometers used for surface test use Zernike polynomials to fit the surface shape [8][9][10].…”

A Microlens Super-Surface Film with Regular Graded Circular Hole-Like Subwavelength Structures for Highly Focusing Strength

“…A study explored a similar low-loss dielectric micro-lens with a nanopillar array with a variable diameter for infrared (IR) radiation on a silicon substrate [18]. Additionally, an antireflective optical lens with large-area glass nanohole arrays for optical imaging was reported [19,20]. However, most reports have not discussed the study of the focusing performance of micro-lens super-surface [21][22][23], which is extremely important to improve the energy utilization.…”